Field of the Invention
The present invention relates to a device for needling a fibrous.
Description of Related Art
A device of the generic kind is disclosed in DE 10 2005 012 265 A1.
The device disclosed therein is used for strengthening and structuring fibrous layers. For this purpose, a fibrous web is pierced with a plurality of needles guided in an oscillating movement. During this process, the needles are guided with an oscillating vertical movement in order to strengthen the fibrous material contained in the fibrous web. During this process, the fibrous web is continuously moved forward by means of an advancing motion preferably carried out by means of rollers. Since the needles are not smooth but are provided with barbed hooks that are open in the piercing direction, individual fibers of the fibrous web are caught and realigned within the fibrous layers when the needles pierce the latter. This results in the desired fiber-mingling and bonding effects within the fibrous web. In order to prevent any undesirable deformations resulting, for example, in a draft of or slots in the needled fibrous material due to the advance of the fibrous web when the needles pierce the latter, the needles are guided in a horizontal movement that is superimposed on the vertical movement.
In the device disclosed in the aforementioned document, both the vertical and the horizontal movements of the needle beam are initiated by means of a crank mechanism drive. For this purpose, the crank mechanism drive comprises two crank drives having two driven crankshafts. By means of a phase-adjusting device, the crankshafts are formed so as to be adjustable in terms of their phase positions. Depending on the phase position of the crankshafts relative to each other, there thus results an ellipsoidal movement pattern, in which an oscillating movement of the needle beam is carried out.
In order to achieve the most stable possible piercing action of the needles into the fibrous web, a guiding device is additionally provided that engages the needle beam. However, in doing so, it is necessary to carry out the vertical and horizontal movements of the needle beam without any obstruction. In the device disclosed in the aforementioned document, the guiding device is formed by a guide rod that is guided on a guide bushing held on a machine frame. The guide bushing is held on the machine frame so as to be pivotable by means of a pivot bearing so that an inclined position of the beam carrier is possible by means of the pivot bearing of the guiding device depending on the phase position of the crankshafts. Depending on the degree of phase adjustment, there thus result various inclined positions of the beam carrier each of which leads to a horizontal movement with a defined stroke. The guide track of the beam carrier is determined by the fixed position of the pivot bearing of the guiding device. Thus, only relatively small horizontal strokes can be carried out since otherwise an excessive inclination of the beam carrier is achieved.
In principle, devices are also disclosed in the prior art in which the vertical movement of the needle beam is carried out by means of a vertical drive and the horizontal movement is carried out by means of a separate horizontal drive. Such a device is disclosed in DE 197 30 532 A1 by way of example. The separate horizontal drive of the device disclosed therein indeed enables larger amplitudes of motion in the horizontal direction, but suffers from the shortcoming of complicated mechanics resulting in insufficient stability and insufficient guidance of the needle beam, particularly at higher throughput speeds.
It is therefore the object of the invention to develop a device for needling a fibrous web of the generic kind such that the superimposed vertical and horizontal movements of the needle beam that are produced by a crank mechanism drive can be carried out with flexible adjustments in amplitudes of motion and stable guidance of the needle beam.